The present invention relates to a vehicle gas-directing component, and more particularly to a non-metallic exhaust manifold with an inner surface having a plurality of embedded ceramic members.
Various types of exhaust manifolds have been used in the field of internal combustion engines. Known exhaust manifolds are typically manufactured of a heat resistance metal such as cast iron to resist the high temperature exhaust gas emitted from the vehicle engine. However, these known manifolds are relatively heavy and tend to absorb much of the thermal energy generated by the exhaust gases.
In order to reduce their weight, some known exhaust manifolds are constructed of a light metal such as aluminum. When using such a material for an exhaust manifold, it becomes necessary to line or coat the inner surface with a heat insulating material such as a ceramic. In one known exhaust manifold, a ceramic fiber layer coats the inner surface of the aluminum exhaust manifold. However, because of the great difference in the thermal expansion properties of metals and ceramics, prolonged use tends to induce undesirable separation of the ceramic layer from the metallic surface. Separation of the ceramic fiber layer typically results in the destruction of the light metal surface by the high temperature exhaust gas.
Known iron exhaust manifolds have a high thermal conductivity and tend to immediately absorb much of the thermal energy generated by the exhaust gases. High thermal conductivity can be a disadvantage as the exhaust system catalyst can not immediately "light off" and a high percentage of total emissions occur before the catalysts are active. It would therefore be further desirable to prevent the exhaust manifold from absorbing the heat of the exhaust gases and allow the residual heat to activate the downstream catalytic converter. The catalytic converter will then "light off" earlier and will operate with higher efficiency which may effectively reduce the emission levels of the engine.
Accordingly, it is desirable to provide a lightweight vehicle gas-directing component which can resist the highly heated exhaust gas emitted from the vehicle engine.